function bbp_buddypress_mark_notifications( $action = '' ) {

	// Bail if no topic ID is passed
	if ( empty( $_GET['topic_id'] ) ) {
		return;
	}

	// Bail if action is not for this function
	if ( 'bbp_mark_read' !== $action ) {
		return;
	}

	// Get required data
	$user_id  = bp_loggedin_user_id();
	$topic_id = intval( $_GET['topic_id'] );

	// Check nonce
	if ( ! bbp_verify_nonce_request( 'bbp_mark_topic_' . $topic_id ) ) {
		bbp_add_error( 'bbp_notification_topic_id', __( '<strong>ERROR</strong>: Are you sure you wanted to do that?', 'bbpress' ) );

	// Check current user's ability to edit the user
	} elseif ( ! current_user_can( 'edit_user', $user_id ) ) {
		bbp_add_error( 'bbp_notification_permission', __( '<strong>ERROR</strong>: You do not have permission to mark notifications for that user.', 'bbpress' ) );
	}

	// Bail if we have errors
	if ( ! bbp_has_errors() ) {

		// Attempt to clear notifications for the current user from this topic
		$success = bp_notifications_mark_notifications_by_item_id( $user_id, $topic_id, bbp_get_component_name(), 'bbp_new_reply' );

		// Do additional subscriptions actions
		do_action( 'bbp_notifications_handler', $success, $user_id, $topic_id, $action );
	}

	// Redirect to the topic
	$redirect = bbp_get_reply_url( $topic_id );

	// Redirect
	bbp_redirect( $redirect );
}